Watercraft drive with a rudder propeller

ABSTRACT

A watercraft drive has a double rudder propeller driven by a driving engine via a driving shaft (1), an angular gear (3, 4) and an output transmission shaft (5). A propeller (6, 7) is arranged at each end of the output shaft. A guiding device made of guide blades (8a, 8b) is arranged between the propellers to correct aerodynamic conditions between both propellers (6, 7) and thus to reduce energy losses.

BACKGROUND OF THE INVENTION

The present invention pertains to a watercraft drive with a drivingengine and a double rudder propeller, which is driven by the drivingengine through driving shafts, angular gear and output transmissionshafts, and the propellers are connected to the output shafts in amanner adapted to rotate in unison.

In another previously known propeller arrangement for the drive of awatercraft, two horizontal propeller shafts are arranged at the lowerend of a vertical driving shaft or two vertical driving shafts, whichare surrounded by a housing tube, with insertion of an angular geardrive, and each one of two propellers is arranged to rotate in unison atthe ends of the propeller shafts, which face away from the angular geardrive. The angular gear drive is designed such that an angular gear ofthe angular gear drive is arranged between a lower shaft end or thelower vertical shaft ends of the vertical shafts or the lower verticalshafts and each of the horizontal shafts. The two propeller shafts,which are output transmission shafts at the same time, are arranged onone side of this drive housing, or one of the propeller shafts isarranged on each side of the drive housing and is led out of the drivehousing correspondingly. If both propeller shafts and thus bothpropellers are arranged on one side of the drive housing, then one ofthese shafts surrounds the other concentrically like a hollow shaft. Thetwo propellers have different designs, especially in the respect thatthe direction of rotation and the diameter of the propellers, but alsoprobably the number of blades, are different at any rate (GB 2 190 344).

Finally, another state of the art (German Patent DE 35 08 203) dealswith an embodiment of a guiding device for a watercraft drive, which isequipped with a propeller, to increase the thrust or to reduce theconsumption of fuel and therefore affects the present invention, at themost, in features that practically embody the present invention

A watercraft drive of this type is known from DE 870 655. The output ofthe driving engine, arranged inside the hull, is introduced into avertically arranged driving shaft, the lower end of which is guidedthrough the bottom of the watercraft towards the outside of the hull,drives horizontally arranged output shafts via an angular gear there,each of which has a propeller that is utilized for the propulsion of thewatercraft at each end facing away from the angular gear. It is alsopossible to design such an arrangement as a rudder propeller, in thatnot only is the drive output introduced at the upper end of thevertically arranged shaft, but an actuator may also be activated, sothat a jacket tube, which surrounds the drive shaft concentrically, ispivotable by up to 360° or all around the longitudinal axis of thedriving shaft. If the actuator is activated, then the propellers areultimately pivoted about the longitudinal axis of the driving shaft andnot only is the output of the driving engine converted to thrust power,but it is possible to use the drive output for maneuvering thewatercraft by means of pivoting the underwater part of the drive systemby 360° as well. In the prior-art device, an angular gear and an outputshaft are assigned to each propeller. Thus, both propellers can bedriven independently of one another. However, the technical cost of thisdrive is not in proportion to the benefit that can be achieved from theseparate operation of the two propellers.

SUMMARY OF THE INVENTION

The basic object of the present invention is to develop a watercraftdrive of the type mentioned in the introduction, which has a simpledesign in terms of production technology, while contributing a highefficiency.

The object is accomplished with the features of claim 1 according to thepresent invention.

Here, both propellers are operated in a functionally identical mannerwith only one angular gear and one line of driving shafts. Thus, adrive, with which the structural volume is also markedly reduced, iscreated, which is considerably simpler and less susceptible comparedwith the state of the art.

With the guiding device, energy losses generated by cavitation, are, toa large extent, prevented, in that the guiding device adjusts thepost-angular momentum that is produced by the front propeller and thusrecovers lost energy.

A guiding device is known from DE 293 611; however, in this case, it isa propeller arrangement with a horizontal driving shaft, i.e., apropeller system without a rudder function.

The angular gear and the output shaft are, as a rule, surrounded by ahousing that is simultaneously used to store the output shaft and theangular gear. According to one embodiment of the present invention, thishousing forms an integral unit with the guiding device, while thehousing tube surrounding the driving shaft is preferably designed as aguide blade. Thus, the area between the two propellers is used for aneffective guiding device in an aerodynamically optimal manner.

The guiding device may, in a simple embodiment, be formed from two guideblades, which are arranged 180° about the axis of rotation of thepropellers and extend radially from the axis of rotation of thepropellers. Of course, it is also possible to provide more than twoguide blades, which are arranged in a rotationally symmetrical mannerabout the axis of rotation of the propellers.

The guide blades preferably have curved lifting surface profiles, and itproves to be very aerodynamically favorable if the curvature is apre-angular momentum curvature and a post-angular momentum curvature.The post-angular momentum of the front propeller can thus be adjustedeffectively and the energy lost during the post-angular momentum due tothe propulsion force produced during the circulation of the guide bladescan be recovered again.

To utilize the action of the guide blades as much as possible, thelengthwise extension of the guide blades is, to a large extent, set toequal the radius of the peak circular movement of the propellers.

DESCRIPTION OF THE DRAWINGS

The present invention is described in detail based on the exemplaryembodiments of the invention schematically shown in the drawing. In thedrawing,

FIG. 1 shows the longitudinal section of the lower end of a drive,

FIG. 2 shows a section according to the line II--II in FIG. 1,

FIG. 3 shows a section according to the line III--III in FIG. 1,

FIG. 4 shows a section according to the line IV--IV in FIG. 1, and

FIG. 5 shows another example of the guiding device.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a watercraft drive that is designed as a double rudderpropeller having a driving engine 20 arranged in the hull 22 withvertical driving shaft 1 and drive propellers outside of the hull 22.

The driving engine 20 which consists of a motor and gears acts on theupper end of the vertical driving shaft 1 in order to cause the drivingshaft 1 to rotate about its longitudinal axis 2 at a variable speed. Theinput bevel gear 3 of an angular gear drive 3, 4, which activelycommunicates with the output bevel gear 4 of the angular gear 3, 4, isadapted to rotate in unison at the lower end of the driving shaft. Theoutput bevel gear 4 has a horizontal output shaft 5 extending in bothdirections, which is adapted to rotate in unison, on each of the freeends of which a propeller 6, 7 is arranged to rotate in unison. Thepropellers will generally have different designs, although peak circularmovements 14 having the same diameter, as well as similar bladegeometries may be possible. Due to the common assignment to the outputshaft 5, they have the same direction of rotation and the same speed,and flow, e.g., in the same direction according to the arrow A.

The angular gear 3, 4 is surrounded by a housing 9, in which the saidoutput shaft 5 is rotatably mounted by means of two bearings 10, 11.This housing 9 is supported by a housing tube 9a, which surrounds thevertical drive axis 1 concentrically and can be pivoted about itslongitudinal axis for the rudder function.

The underwater part of the drive system is able to be arranged within anozzle 12.

The front propeller 6 produces a residual or post-angular momentum inits wake, which represents lost energy. The propeller 7, which isarranged downstream and rotates in the same direction, is impacted on bythe wake of the front propeller. Without a guiding device between thetwo propellers 6, 7, the above-mentioned unfavorable wake would lead toincreased cavitation and an increase in the energy losses.

To actively oppose this energy loss, a guiding device 8, with which thepost-angular momentum of the front propeller 6 is adjusted, is providedbetween the two propellers 6, 7. Lost energy is recovered, in that apropulsion force is produced during the circulation of the guidingdevices. In addition, a pre-angular momentum is produced for thepropeller 7 arranged downstream, so that this propeller is able toreverse a higher energy drop. Taking this criterion into account, thesecond propeller 7 will preferably have a structural design that isdifferent from the first propeller 6.

According to FIG. 1 the guiding device 8 comprises two guide blades 8aand 8b, whereby one guide blade 8a is formed by the housing tube 9asurrounding the vertical driving shaft 1. The second guide blade 8b isarranged on the underside 9b of the housing 9 surrounding the horizontaloutput shaft 5, i.e., offset by 180° from the first guide blade, and hasa free edge distal from the housing 9. The two guide blades 8a, 8b forma structural unit with the entire housing 9, 9a.

FIGS. 2 and 3 each show a cross section of the upper guide blade 8a andthe lower guide blade 8b, respectively. According to them, the guideblades 8a, 8b have curved lifting surface profiles, which have apre-angular momentum curvature α to deflect the flow for the secondpropeller 7 and a post-angular momentum curvature β to adjust thepost-angular momentum of the first propeller 6.

The lengthwise extension L of the guide blades 8a, 8b corresponds, as isshown in FIG. 4, to the radius R of the peak circular movement 14 of thepropellers 6, 7.

FIG. 5 shows another example of a guiding device in a section that isidentical to that in FIG. 4. In this example, three instead of two guideblades 15, 16, 17 are provided in rotationally symmetrical arrangementabout the common axis of rotation 18 of both propellers 6, 7. Of course,the guiding device may also consist of more than three guide blades.

What is claimed is:
 1. A drive for a watercraft for travel on a body ofwater, said watercraft having a hull and a driving engine, a drive shaftoperatively connected to said driving engine, a housing having avertical section surrounding said drive shaft and a horizontal section,an angular gear having input means operatively connected to said driveshaft and output means, an output shaft operatively connected to saidangular gear output means, said horizontal section circumscribing saidangular gear and a length of said output shaft connected thereto, afirst propeller mounted on one end of said output shaft outside of saidhorizontal section and a second propeller mounted on the other end ofsaid output shaft outside of said horizontal section for rotation inunison, and a guiding device mounted between and spaced from thepropellers, for reducing cavitation and increasing the efficiency ofsaid drive, said guiding device comprising a plurality of blades one ofwhich is integral with said housing vertical section, and at leastanother of which has an edge connected to said housing horizontalsection and an opposite free edge.
 2. A drive in accordance with claim 1wherein the guiding device comprises at least two guide blades inrotationally symmetrical arrangement about the common axis of rotationof said first and second propellers, each of said guide blades having acurved lifting surface.
 3. A drive in accordance with claim 1, whereinthe radial lengthwise extension (L) of the guide blades correspondsapproximately to the radius (R) of the peak circular movement of thepropellers.
 4. A drive in accordance with claim 1 further comprising anozzle mounted on said housing, part of the drive extending outside ofthe hull and being disposed within said nozzle.